ANIMAL AND VEGETABLE PHYSIOLOGY. 
621 
triangle, and the body is consequently still supported on these 
three°feet. The fore foot may now be advanced without endan¬ 
gering the stability of the body; and by the time the foot is set 
down, the centre of gravity has arrived above the centre of this 
new base. But at this moment the centre of gravity is again 
urged forwards by the other hind foot, which now comes into 
action, and repeats, on the other side, the same succession of 
actions, which are attended with the same consequences as 
before. 
“ In quick walking, it often happens that quadrupeds, parti¬ 
cularly fast walking horses, raise their fore foot on either side a 
little before the hind foot comes to the ground: such horses are 
very liable to fall; but, generally speaking, the time during 
which the body is thus supported only by two feet is so short 
as not sensibly to influence the results. 
“ A trot may be considered as a succession of short leaps made 
by each set of feet diagonally; that is, by the right fore foot 
and the left hind foot; or, vice versa , the one set being raised 
together a short time before the others have reached the ground; 
so that during that minute interval of time all the feet are in 
the air at the same moment; and during the remaining portion 
of the time, the body is resting upon the two feet placed dia¬ 
gonally with regard to each other. The undulations are here 
chiefly vertical, instead of lateral, as they are in the walking 
pace. 
“ A gallop is a continued succession of longer leaps made by 
the two hind feet in conjunction. In this case the centre of 
gravity is lifted higher from the ground, and is projected on a 
wide arch, and with great velocity.” 
We have thus followed the author in his description of the 
three paces, walk , trot , and gallop , being those most particularly 
interesting to veterinarians. Nature has purposely endowed dif¬ 
ferent tribes with different capacities to execute progressive 
movements, by the variations she has introduced into the com¬ 
parative lengths of the several parts of the trunk, and the size 
and mobility of the extremities. It would exceed our limits to 
accompany him farther on this subject, and we will proceed to 
another, viz. 
Perceptions of Animals . 
The more an organ of sense differs in its structure from those 
which we ourselves possess, the more uncertain must be our 
knowledge of its functions. We may, indeed, without any great 
stretch of fancy, conceive ourselves placed in the situation of 
the beasts of the forests, and comprehend what are the feelings 
VOL. VII, 4 l 
